The edge coloring of a pentagon is as shown in Figure 1
b
|
1
/ \
r g
/ \
b--5 2--r
| |
g b
| |
4---y---5
/ \
r r
Figure 1.
IS THIS GRAPH THREE EDGE COLORABLE?
A A 4
|----------------------------------| B 8
| \ B / | C 5
| |--|--------|-----|-------|--| | D 5
| | | | C | | | | E 5
| | | D |--|--| E | | | F 5
| | | / | \ | | | G 5
| |F |-----| G | H |-----| I| | H 5
| | | \ | / | | | I 5
| | | |--|--| | | | J 5
| | | | J | | | | K 5
|K |--| L |-----| M |--| N| L 8
| | | | O | | | | M 8
| | | |--|--| | | | N 5
| | | / | \ | | | O 5
| |P |-----| Q | R |-----| S| | P 5
| | | \ | / | | | Q 5
| | | T |--|--| U | | | R 5
| | | | V | | | | S 5
| |--|--------|-----|-------|--| | T 5
| / W \ | U 5
|----------------------------------| V 5
W 8